Expeditor

Expeditor is a Ruby library that provides asynchronous execution and fault tolerance for microservices.

It is inspired by Netflix/Hystrix.

Installation

Expeditor currently supports Ruby 2.1 and higher.

Add this line to your application's Gemfile:

gem 'expeditor'

And then execute:

$ bundle

Or install it yourself as:

$ gem install expeditor

Usage

asynchronous execution

command1 = Expeditor::Command.new do
  ...
end

command2 = Expeditor::Command.new do
  ...
end

command1.start # non blocking
command2.start # non blocking

command1.get   # wait until command1 execution is finished and get the result
command2.get   # wait until command2 execution is finished and get the result

asynchronous execution with dependencies

command1 = Expeditor::Command.new do
  ...
end

command2 = Expeditor::Command.new do
  ...
end

command3 = Expeditor::Command.new(dependencies: [command1, command2]) do |val1, val2|
  ...
end

command3.start # command1 and command2 are started concurrently, execution of command3 is wait until command1 and command2 are finished.

fallback

command = Expeditor::Command.new do
  # something that may be failed
end

# use fallback value if command is failed
command_with_fallback = command.set_fallback do |e|
  log(e)
  default_value
end

command.start.get #=> error may be raised
command_with_fallback.start.get #=> default_value if command is failed

If you set false to Expeditor::Service#fallback_enabled, fallbacks do not occur. It is useful in test codes.

timeout

command = Expeditor::Command.new(timeout: 1) do
  ...
end

command.start
command.get #=> Timeout::Error is raised if execution is timed out

retry

command = Expeditor::Command.new do
  ...
end

# the option is completely same as retryable gem
command.start_with_retry(
  tries: 3,
  sleep: 1,
  on: [StandardError],
)

using thread pool

Expeditor use concurrent-ruby's executors as thread pool.

require 'concurrent'

service = Expeditor::Service.new(
  executor: Concurrent::ThreadPoolExecutor.new(
    min_threads: 0,
    max_threads: 5,
    max_queue: 100,
  )
)

command = Expeditor::Command.new(service: service) do
  ...
end

service.current_status
# => #<Expeditor::Status:0x007fdeeeb18468 @break=0, @dependency=0, @failure=0, @rejection=0, @success=0, @timeout=0>

service.reset_status!  # reset status in the service

circuit breaker

service = Expeditor::Service.new(
  period: 10,          # retention period of the service metrics (success, failure, timeout, ...)
  sleep: 1,            # if once the circuit is opened, the circuit is still open until sleep time is passed even though failure rate is less than threshold
  threshold: 0.5,      # if the failure rate is more than or equal to threshold, the circuit is opened
  non_break_count: 100 # if the total count of metrics is not more than non_break_count, the circuit is not opened even though failure rate is more than threshold
)

command = Expeditor::Command.new(service: service) do
  ...
end

synchronous execution

Use current_thread option of #start, command executes synchronous on current thread.

command1 = Expeditor::Command.new do
  ...
end

command2 = Expeditor::Command.new do
  ...
end

command1.start(current_thread: true) # blocking
command2.start(current_thread: true) # blocking

command1.get
command2.get

Development

After checking out the repo, run bin/setup to install dependencies. Then, run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release to create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

1. Fork it ( https://github.com/cookpad/expeditor/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request